Use of polyethylene compositions

Abstract

The use in the manufacture of a polyethylene article of a polyethylene composition comprising 20 to 50% wt of a copolymer of ethylene and a C 3-20 alpha olefin comonomer and 50 to 80% wt. Of a lower weight average molecular weight ethylene polymer, the polyethylenes of the composition together having a density of 935 to 965 kg/m 3 , weight average molecular weight of 60000 to 300000 g/mol, an MFR 2.16 at 190° C. of 0.1 to 10 g/10 min., and a molecular weight distribution (MWD) of from 2.5 to 20, the copolymer having a comonomer content of from 0.006 to 9 mol % and a degree of branching of 0.03 to 45 branches per 1000 carbons, and the ethylene polymer having a density of 939 to 975 kg/m 3 and a weight average molecular weight of 20000 to 200000 g/mol.

1 . A polyethylene composition comprising 20 to 40% wt of a copolymer of ethylene and a C 3-20  alpha olefin comonomer and 60 and 80% wt of a lower weight average molecular weight ethylene polymer, the polyethylenes of said composition together having a density of 935 to 965 kg/m 3 , a weight average molecular weight of 60000 to 300000 g/mol, an MFR 2.16  at 190° C. of 0.1 to 10 g/10 min., and a molecular weight distribution (MWD) of from 2.5 to 10, said copolymer having a comonomer content of from 0.006 to 9 mol % and a degree of branching of 0.03 to 45 branches per 1000 carbons, and said polymer having a density of 939 to 975 kg/m 3  and a weight average molecular weight of 20000 to 200000 g/mol.  
   
   
       2 . A polyethylene composition as claimed in  claim 1  wherein said composition is free of long chain branching.  
   
   
       3 . A polyethylene composition as claimed in  claim 1  wherein said copolymer is produced using an unbridged bis-cyclopentadienyl metallocene catalyst.  
   
   
       4 . A composition as claimed in  claim 1  having an eta 300 value of 500 to 1500 Pa·s and an eta 0.05 value of 1300 to 80000 Pa·s.  
   
   
       5 . A composition as claimed in  claim 1  having an eta 300 value of less than 1000 Pa·s and an eta 0.05 value of less than 130000 Pa·s.  
   
   
       6 . A process for the production of a polyethylene article which comprises extruding, casting or moulding a polyethylene composition comprising 20 to 40% wt of a copolymer of ethylene and a C 3-20  alpha olefin comonomer and 60 and 80% wt of a lower weight average molecular weight ethylene polymer, the polyethylenes of said composition together having a density of 935 to 965 kg/m 3 , a weight average molecular weight of 60000 to 300000 g/mol, an MFR 2.16  at 190° C. of 0.1 to 10 g/10 min., and a molecular weight distribution (MWD) of from 2.5 to 10, said copolymer having a comonomer content of from 0.006 to 9 mol % and a degree of branching of 0.03 to 45 branches per 1000 carbons, and said polymer having a density of 939 to 975 kg/m 3  and a weight average molecular weight of 20000 to 200000 g/mol.  
   
   
       7 . A process as claimed in  claim 6  wherein said copolymer is produced by polymerization of ethylene and a C 3-20  alpha olefin comonomer catalysed by an unbridged bis-cyclopentadienyl metallocene catalyst.  
   
   
       8 . A process as claimed in  claim 6  which comprises blow moulding said composition.  
   
   
       9 . A method of manufacturing a polyethylene article which comprises the step of using a polyethylene composition comprising 20 to 40% wt of a copolymer of ethylene and a C 3-20  alpha olefin comonomer and 60 and 80% wt of a lower weight average molecular weight ethylene polymer, the polyethylenes of said composition together having a density of 935 to 965 kg/m 3 , a weight average molecular weight of 60000 to 300000 g/mol, an MFR 2.16  at 190° C. of 0.1 to 10 g/10 min., and a molecular weight distribution (MWD) of from 2.5 to 10, said copolymer having a comonomer content of from 0.006 to 9 mol % and a degree of branching of 0.03 to 45 branches per 1000 carbons, and said polymer having a density of 939 to 975 kg/m 3  and a weight average molecular weight of 20000 to 200000 g/mol.  
   
   
       10 . The method according to  claim 9  wherein step of using said polyethylene article is by blow moulding said polyethylene composition.